1. Field of the Invention
The present invention relates generally to supersaturating a liquid with a gas containing oxygen and more specifically to a method of treating a liquid by counter current supersaturation oxygenation, which enables oxygen supersaturation of the liquid.
2. Discussion of the Prior Art
U.S. Pat. No. 3,643,403 to Speece discloses a downflow bubble contact aeration apparatus and method. The Speece patent includes the aeration of oxygen deficient water by dispersing bubbles of air or oxygen gas in a forced downflow of water through a downwardly diverging funnel trapping the bubbles therein for a prolonged contact with water. However, Speece must use water under pressure to properly oxygenate the water.
U.S. Pat. No. 4,217,211 to Crane discloses a pressurized treatment of sewage. The Crane patent includes passing a liquor of the sewage into a subterranean shaft through an inner shaft, which extends only partway down into a deep subterranean shaft. A mixing shaft is located at a lower proximity of the inner shaft. The descending sewage liquor passes downwardly through the mixing nozzles to the bottom of the subterranean shaft.
U-tubes are known in the art and include a vertical shaft 30-150 feet deep, which is either partitioned into two sections or consisting of two concentric pipes. Oxygen is sparged at the top of the down-leg of the U-tube and is transferred into a gas-liquid mixture. The gas-liquid mixture exits an up-leg of the U-tube. However, U-tubes oxygenate a water stream at a top of the intake, which results in less efficient oxygenation of the water stream.
It is more efficient to treat waste water using oxygen instead of using normal air. For example, oxygen provides superior activation of the bacteria and protozoans used in activated sludge.
Accordingly, there is a clearly felt need in the art for a method of treating a liquid by counter current supersaturation oxygenation, which enables a more efficient oxygen supersaturation of the liquid than that of the prior art and which does not require the use of pressurized water.